我不确定为什么会收到此错误，我正在运行一个隐写程序，该程序会接收一个PPM文件，并允许用户将消息编码到PPM文件中，并且尝试在valgrind中进行调试，并且发生错误：
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
struct PPM {
char *comments;
char *ppmname;
unsigned int width, height, max;
unsigned int size;
struct Pixel**pixels;
}ppm;
struct Pixel {
int r, g, b;
}Pixel;
static int *decimalToBinary(const char *message, unsigned int msgSize);
struct PPM * getPPM(FILE * f);
struct PPM *encode(struct PPM *im, char *message, unsigned int mSize, unsigned int secret);
void showPPM(struct PPM * im);
int main(int argc, char *argv[]){
FILE * fin = fopen("home-cat.ppm", "r");
if(fin == NULL) {
perror("Cannot open file");
exit(1);
}
struct PPM *p = getPPM(fin);
struct PPM *g = encode(p, "test", 5, 2);
showPPM(g);
free(p->comments);
free(p);
return 0;
}
struct PPM * getPPM(FILE * f) {
ppm.comments = (char *)calloc(70,sizeof(char));
ppm.ppmname = (char *)calloc(3,sizeof(char));
fscanf(f, "%s", ppm.ppmname);
fgetc(f);
fgets(ppm.comments, 70, f);
fscanf(f, "%d %d", &ppm.width, &ppm.height);
fscanf(f, "%d", &ppm.max);
ppm.size = ppm.width * ppm.height;
ppm.pixels = (struct Pixel**)malloc(ppm.width * sizeof(struct Pixel));
for (int i=0; i<ppm.width; i++) {
ppm.pixels[i] = (struct Pixel*)malloc(ppm.height*sizeof(struct Pixel));
}
for (int i=0; i<ppm.width; i++) {
for (int j=0; j<ppm.height; j++) {
fscanf(f, "%d %d %d", &ppm.pixels[i][j].r, &ppm.pixels[i][j].g, &ppm.pixels[i][j].b);
}
}
return &ppm;
}
void showPPM(struct PPM * im) {
printf("%s\n", ppm.ppmname);
printf("%s", ppm.comments);
printf("%d %d\n", ppm.width, ppm.height);
printf("%d\n", ppm.max);
for (int i=0; i<ppm.width; i++) {
for (int j=0; j<ppm.height; j++){
printf("%d %d %d\n", ppm.pixels[i][j].r, ppm.pixels[i][j].g, ppm.pixels[i][j].b);
}
}
}
struct PPM *encode(struct PPM *im, char *message, unsigned int mSize, unsigned int secret) {
int *binaryMessage = decimalToBinary(message, mSize);
int i, j, k;
bool unique;
srand(secret);
int used[40]; memset(used, -1, sizeof(used)); // might have the last two args backwards... I always forget lol
for(i = 0; i < 39; i+=3) {
// determine next pixel based on the user's secret (srand)
// and without ovewrwriting a previous hidden message
do {
unique = true;
j = rand() % 3; // get new number and then check if it's unique
for(k = 0; k < i; k++) if (used[i] == j) {unique = false; break;}
} while(!unique);
im->pixels[j]->r = im->pixels[j]->r & ~1 | binaryMessage[i+0]; // ~1 is 11111110
im->pixels[j]->g = im->pixels[j]->g & ~1 | binaryMessage[i+1]; // anding keeps the first 7 and clears the last
im->pixels[j]->b = im->pixels[j]->b & ~1 | binaryMessage[i+2]; // oring will set it if the binaryMessage is set
}
// should make a function...
do {
unique = true;
j = rand() % 3; // get new number and then check if it's unique
for(int k = 0; k < 39; k++) if (used[i] == j) {unique = false; break;}
} while(!unique);
im->pixels[j]->r = im->pixels[j]->r & ~1 | binaryMessage[39]; // last bit
free(binaryMessage);
return im;
}
static int *decimalToBinary(const char *message, unsigned int length) {
/*
* malloc is used here instead of [] notation to allocate memory,
* because defining the variable with [] will make its scope
* limited to this function only. Since we want to access this
* array later on, we use malloc to assign space in the memory
* for it so we can access it using a pointer later on.
*/
int k = 0, i, j;
unsigned int c;
unsigned int *binary = malloc(8 * length * sizeof(int));
for(i = 0; i < length; i++) {
c = message[i];
for(j = 7; j >= 0; j--,k++) {
/*
* We check here if the jth bit of the number is 1 or 0
* using the bit operator &. If it is 1, it will return
* 1 because 1 & 1 will be true. Otherwise 0.
*/
if((c >> j) & 1)
binary[k] = 1;
else
binary[k] = 0;
}
}
return binary;
}
我不确定为什么会这样，所以我在valgrind内部运行错误，因为我在线阅读了这是一个非常有用的调试器，但是我仍然无法理解问题的根源。这是valgrind中的错误报告：
==2066== Invalid free() / delete / delete[] / realloc()
==2066== at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2066== by 0x108B14: main (in /home/ziyad/test12)
==2066== Address 0x30a060 is 0 bytes inside data symbol "ppm"
==2066==
==2066==
==2066== HEAP SUMMARY:
==2066== in use at exit: 2,150,955 bytes in 515 blocks
==2066== total heap usage: 519 allocs, 5 frees, 2,156,305 bytes allocated
==2066==
==2066== 3 bytes in 1 blocks are still reachable in loss record 1 of 4
==2066== at 0x4C31B25: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2066== by 0x108B4D: getPPM (in /home/ziyad/test12)
==2066== by 0x108AC8: main (in /home/ziyad/test12)
==2066==
==2066== 552 bytes in 1 blocks are still reachable in loss record 2 of 4
==2066== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2066== by 0x4EBAE49: __fopen_internal (iofopen.c:65)
==2066== by 0x4EBAE49: fopen@@GLIBC_2.2.5 (iofopen.c:89)
==2066== by 0x108A9B: main (in /home/ziyad/test12)
==2066==
==2066== 6,144 bytes in 1 blocks are still reachable in loss record 3 of 4
==2066== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2066== by 0x108C0E: getPPM (in /home/ziyad/test12)
==2066== by 0x108AC8: main (in /home/ziyad/test12)
==2066==
==2066== 2,144,256 bytes in 512 blocks are still reachable in loss record 4 of 4
==2066== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2066== by 0x108C53: getPPM (in /home/ziyad/test12)
==2066== by 0x108AC8: main (in /home/ziyad/test12)
==2066==
==2066== LEAK SUMMARY:
==2066== definitely lost: 0 bytes in 0 blocks
==2066== indirectly lost: 0 bytes in 0 blocks
==2066== possibly lost: 0 bytes in 0 blocks
==2066== still reachable: 2,150,955 bytes in 515 blocks
==2066== suppressed: 0 bytes in 0 blocks
==2066==
==2066== For counts of detected and suppressed errors, rerun with: -v
==2066== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
ppm是一个堆栈对象，而不是堆分配的对象。您不应该释放它。您只能调用free()先前由malloc()或返回的指针calloc()。这里不是这种情况，所以不是free()。
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